The present invention generally relates to an information retrieval apparatus and more particularly, to an automatic retrieval apparatus for films containing information therein such as microfilms and the like.
Commonly, for the automatic retrieval of a microfilm in a roll form, count marks generally referred to as document marks or blips are provided in positions corresponding to respective frames of the microfilm so as to retrieve required frames by counting said document marks.
The microfilms of the above described type are broadly divided into a one channel type in which a plurality of frames 2-1, 2-2, 2-3, and . . . 2-n are aligned in one row on a microfilm 1, with document marks 3-1, 3-2, 3-3, and . . . 3-n being provided between the respective frames and one side edge of the microfilm 1 as shown in FIG. 1, and into a two channel type in which frames 4-1, 4-2, 4-3, and . . . 4-n, and 5-1, 5-2, 5-3, and . . . 5-n are respectively provided in two rows as shown in FIG. 2 to provide a lower channel or A channel and an upper channel or B channel, while document marks 6-1, 6-2, 6-3, and . . . 6-n, and 7-1, 7-2, 7-3, and . . . 7-n are provided between one edge of the microfilm 1' and the respective frames 5-1, 5-2, 5-3, and . . . 5-n for the channel A and also between the other edge thereof and the respective frames 4-1, 4-2, 4-3, and . . . 4-n for the channel B so as to effect independent retrieval for each channel or simultaneous retrieval for both channels. Depending on requirements, some microfilms have an interval or pitch between the respective frames reduced or narrowed as shown in FIG. 2. Meanwhile, the automatic retrieval system utilizing the microfilms as described above has made a rapid progress recently, with the retrieving speed thereof being increased still further, and it is noted that the increased retrieving speed, together with the size of the document marks, has an important bearing on the count operation or the calculation processing time in terms of the control circuitry therefor. On the other hand, following the development of the electronic industry, micro-computers have been put into actual applications for utilization thereof in the automatic retrieval field. In the case as described above, since the program is processed in a serial manner with respect to time, it is necessary to pay attention to the processing time as stated above, with the necessity thereof increasing still more with respect to the document marks for two channels whose width is small as shown in FIG. 2.
FIG. 3 shows a block diagram representing one example of a conventional count processing circuit for document marks employing a micro-computer; upon the projection of light 10 onto the document marks 3 of the microfilm 1, the transmitted light which varies in its intensity is applied to a photosensing element 11, and the electric signal from the photoelectric conversion by the element 11 is amplified by an operational amplifier 12 whose input terminals are connected to the photosensing element 11 and whose output terminal is coupled to a waveform shaping circuit 13; the signal, after being subjected to shaping in the circuit 13, is fed into the micro-computer 14 for counting, calculation, judgement, etc. The micro-computer 14 further includes a central processing unit CPU which is coupled to a read only memory ROM in which programs are stored for sequentially processing counting, calculation, judgement, etc., a random access memory RAM for temporarily storing the information during execution of the programs, and an input and output interface I/O which is coupled to the waveform shaping circuit 13, a motor rotational direction detecting circuit 15, a motor drive control circuit 16 and an external motor M, etc. for controlling inputs and outputs of external control sections. The micro-computer 14 also includes an address decoder AD for selecting each of the sections. A key section 18 is also connected to the input and output interface I/O for keying-in the required frames or numbers, and a displaying section 19 is connected to interface I/O for the indication thereof.
The signal subjected to the waveform shaping is passed through the input and output interface I/O so as to be used as a count signal by the program stored in the micro-computer 14, and after the count calculation is performed in the micro-computer 14, the count signal is applied, through the input and output interface I/O, to the motor rotational direction detecting circuit 15 and to the motor drive control circuit 16 in the form of a motor running and stopping signal 17 which also serves as a motor stopping timing signal.
Reference is also made to FIG. 4 showing a time chart related to the count calcuation in the microfilm retrieval apparatus employing the micro-computer as described above. Generally, edge portions (i.e. rising or falling portions) of the photoelectric signal are adopted for count timing, and the micro-computer 14 detects the variation thereof and enters the count and calculation program routine. In the process described above, even when variation of the document marks for the channel B takes place during the same period of time or during a count calculation of the document marks for the channel A, it can not be read due to the overlapping shown by the dotted lines in FIG. 4. Therefore, it becomes necessary to positionally displace the document marks themselves or the photosensing element itself with respect to the running direction of the film by an amount equivalent to the time period required for calculating the signal of the document marks for the channel A and the signal of the document marks for the channel B. Alternatively, there may be employed another method in which a counter is provided in each of the A and B channels for supplying an output thereof to the micro-computer. The conventional arrangements as described above, however, have disadvantages in that the former is not suitable for general purposes, with requirements for positional adjustments, while the latter invites complications in the construction of the apparatus, with a consequent increase in its cost.